1. Field of the Invention
The present invention relates to a hydrostatic continuously variable transmission which is assembled with improved workability.
2. Description of Background Art
A hydrostatic continuously variable transmission has been known as a continuously variable transmission for a motorcycle or an automobile. Such a continuously variable transmission is disclosed in Japanese Examined Patent Publication No. 7-56340 and Japanese Unexamined Patent Publication No. 4-203553. Its schematic configuration is illustrated in FIG. 4.
As shown in FIG. 4, this hydrostatic continuously variable transmission has a fixed displacement type swash plate hydraulic pump P connected to the crank shaft side of an engine and a variable displacement type swash plate hydraulic motor M connected to a driving wheel side. The hydraulic pump P and the hydraulic motor M are connected to each other to constitute a hydraulic closed circuit via an inside oil passage (low pressure passage) 52 which is a low pressure passage in a normal load operation but is a high pressure passage in a speed reducing operation, that is, in a reverse load operation and an outside oil passage (high pressure passage) 53 which is a high pressure passage in a normal load operation but is a low pressure passage in a reverse load operation. An oil supply passage 47, connected to an oil supply pump 88 sucking oil from an oil reservoir 87, is connected to the inside oil passage 52 via a first check valve 95 and is connected to the outside oil passage 53 via the second check valve 96.
A pressure regulating valve 97 is disposed between the outside oil passage 53 and the inside oil passage 52. When the hydraulic pressure in the outside oil passage 53, which is a high pressure side in a normal load operation, that is, in an acceleration operation, becomes larger than a predetermined value, the pressure regulating valve 97 introduces part of the hydraulic oil in the outside oil passage 53 into the inside oil passage 52 to prevent the hydraulic pressure in the outside oil passage 53 from becoming excessive.
In a hydrostatic continuously variable transmission having the configuration described above, the fixed displacement type swash plate hydraulic pump P has a plate mounted at a predetermined angle with respect to a pump swash plate (input shaft) and many pump plungers (pistons) each of which is slidably fitted in each of many cylinder bores formed in a cylinder block integral with the output shaft and is engaged with the plate at its outside end. The outside end of the pump plunger is engaged with the plate by putting the spherical portion of the outside end of the each pump plunger into contact with the dimple formed on the plate.
On the other hand, in the cylinder block, a valve bore is formed in each cylinder bore in the radial direction and a distributor valve is mounted in the valve bore such that it can move in the radial direction. The cylinder bore is switched between the inside oil passage and the outside oil passage by the reciprocating motion of the distributor valve in the radial direction. The head portion of the distributor valve is driven by a ring like eccentric cam mounted on the pump plate to move the distributor valve. Accordingly, in order for the hydraulic pump to correctly suck and discharge hydraulic oil, it is necessary to correctly mount the pump swash plate on a casing.
Conventionally, the plate is aligned with the pump plunger by the manual work by an operator as follows: the dimple formed on the plate is put into contact with the spherical portion at the top end of the pump plunger by the tactile sense of the operator while rotating the pump swash plate.
However, since the alignment of the plate with the plunger pump is performed by the tactile sense of the operator, the dimple of the plate is sometimes not aligned with the pump plunger. In particular, when an unskilled operator assembles this transmission in a short cycle of time on a mass production line, it takes much time to assemble the transmission because he does not put the pump plunger in the dimple of the plate but puts the pump plunger on the outside the dimple of the plate or the like. This becomes a cause of increased costs.
The configuration of the present invention for solving the above problem includes a hydrostatic continuously variable transmission having a hydraulic closed circuit constituted between a fixed displacement type swash plate hydraulic pump and a variable displacement type swash plate hydraulic motor, an engaging part to be engaged with a positioning jig when the pump swash plate of the hydraulic pump is mounted in a cylinder block integral with an output shaft is provided on the back surface of the plate of the hydraulic pump and the pump swash plate.
According to the hydrostatic continuously variable transmission having the above configuration, since the engaging part to be engaged with a positioning jig when the pump swash plate of the hydraulic pump is mounted in the cylinder block integral with the output shaft is provided on the back surface of the plate of the hydraulic pump and the pump swash plate, when the pump swash plate is mounted, it can be easily positioned and mounted by putting the positioning jig into contact with the back surface of the plate and the pump swash plate.
Further scope of applicability of the present invention will become apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.